No, you did not receive unworthily. Yawning, coughing, sneezing, etc. are involuntary bodily functions. In other words, God designed your body to do them. If what you did constitutes receiving unworthily, then the very fact that you drove to church (thereby soiling your hands on the steering wheel) means you did as well. Or touching the Missal that someone else used before you. Even if you used hand sanitizer before receiving or shaking hands, one could argue that made one "unworthy" as well, because sanitizer is a man-made chemical. Now you have no germs, but you do have chemicals on your hands. Which is worse...? I'm not saying this to make fun of you or add to your burden. Satan loves to keep people from receiving the Eucharist. If he can't do it by having us commit a mortal sin right before Mass so we can't receive, then he'll do it by trying to convince us that we have somehow done something wrong during Mass. The last thing he wants is people in a state of grace receiving the Eucharist. Unless it's people who aren't in a state of grace making a good confession.
I'm not saying we shouldn't show proper respect for the Eucharist. We should. But we shouldn't go over the top, because then we deny the efficaciousness of it. It is the body, blood, soul and divinity of Christ. That's powerful enough to overcome any germs. Besides, no matter what you do, your hands will never be perfectly clean. And even if you receive on the tongue, unless you are the first person to receive from the priest, he's touched other mouths and other tongues before yours. Does that make his hands unclean? Of course not, and no one would think so.
Also, ask yourself, what if the priest did what you did. Would you think him unworthy to receive or distribute the Eucharist? Or would you think perhaps he had been up all night with someone who was dying, yet still came to offer Mass in spite of being exhausted. Probably the latter, right? One litmus test, if you will, whenever you begin to wonder if it's okay for you to receive, just ask yourself, "If it was someone else, would I think they shouldn't receive?" Unless you can come up with a resounding, firm, "No, they shouldn't", then receive. Unless you know you are in a state of Mortal Sin ,which can never *happen "accidently" - you have to *know something is a mortal sin before you do it- then receive. With all the love and reverence you have, receive.